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Phylum Chordata Featuring Vertebrate Animals
Linn-Benton Community College
Characteristics • All have a notochord: a stiff but flexible rod that extends
the length of the body and serves as a point of attachment for the muscles.
• A dorsal, hollow nerve cord - connects to the brain at the anterior end.
• Pharyngeal gill slits which appear at some time in the development of chordates, may form functional respiratory organs in those animals with gills.
• Post-anal tail (at some point in development). • All have deuterstome development.
Human Embryo – features 4 chordate features.
Representative Members I. Invertebrate Chordates Lancelets Tunicates II. Vertebrate Chordates Fish Amphibians Reptiles Birds Mammals
Lack the backbone that is found in vertebrates. Have a nerve cord and all other chordate features.
Jawless fish Hagfishes & Lamphreys - The earliest vertebrate fossils. - Do not have a bony backbone, but rather a flexible nerve
cord & some cartilage
Hagfishes – A jawless fish Least derived craniate lineage that still survives. A slimy character Lack Vertebrae & no jaws. Deep water – Marine Retain Notochord as adults. Class Myxini
Slime glands
Lampreys are jawless vertebrates Inhabiting various marine & freshwater habitats. Have a spinal cord protected by segments of cartilage (tube & projects) - true vertebrate. Parasitic fish.
Class: Petromyzontida
Fish with Jaws
Jaws allowed these animals to grasp food and become better hunters.
I. Cartilaginous fishes - include sharks, skates
& rays. II. Ray-finned fishes - largest group of
vertebrates by number of species (>24,000 identified so far.
- important food source for humans
Chondrichthyes (cartilaginous fishes)
Ray-finned fishes
Some unusually adapted bony fish
Amphibians -Animals that live part of their lives on land and part in the water. - A three chambered heart. - Must lay their eggs in the water, because they are not protected by shells. - Have a thin, permeable skin, subject to water loss &
dehydration, some species respire through the skin. - Some representatives undergo a metamorphosis during
development that includes a larval phase.
Reptiles - Have a tough, scaly skin that resists water loss. - Have internal fertilization of eggs. - Have an amniotic (shelled) egg that encloses a watery
environment during development. - Have a three chambered heart. - Dinosaurs which were the largest reptiles ruled for 150
million years.
Special Adaptations - Protection • All turtles have a boxlike shell
Made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs – they are living bone.
(d) Eastern box turtle (Terrapene carolina carolina)
Birds - Have feathers, which are highly modified and
specialized scales for insulation and flight. - Have adaptations that minimize their weight such
as hollow bones, reduced reproductive organ size in order to fly.
- Have a shelled egg similar to reptiles. - Warm blooded with high metabolic rates. - Efficient respiratory systems that allow the flow of
oxygen at all times through their bodies even during exhalation.
- First appear in the fossil record about 150 mya.
Birds
Some birds are gregarious, meaning that they come together in flocks. This behavior serves two purposes:
- Flocking individuals are safer from predators.
- Family groups that can efficiently scout for food.
Zedcor, Inc. From ClipArt.com
Adaptation - Specialization
Figure 34.31
Grasping bird (such as a woodpecker)
Perching bird (such as a cardinal)
Raptor (such as a bald eagle)
Swimming bird (such as a duck)
Mammals
- Have distinguishing hair or fur for insulation and warmth.
- Have mammary glands that supply milk for the suckling of their young.
- Give birth to live young with the exception of the platypus and echidna.
- Have well developed nervous systems and brains. -Warm blooded with high metabolic rates.
Odd Mammal
The platypus is the exception to the rule.
- It has fur and feeds its young with milky secretions, but it lays eggs.
- This trait suggests a close link with the reptiles from which mammals are derived.
Marsupials
• Marsupials are mammals that have pouches in which they raise their young through early infancy.
• Examples of Marsupials include Koalas, Kangaroos, and Opossums, and Wallabies. Photo from Yahoohoolicans website
Koala Phascolarctos cinereus
Examples of Marsupials
Eutherians (Placental Mammals)
• Compared to marsupials Eutherians have a longer period of pregnancy
• Young eutherians complete their embryonic
development within a uterus joined to the mother by the placenta
Figure 34.37
Diversification of Mammals
Mammals have evolved to fill nearly every niche (role) and habitat (place) on Earth.
Including: > The sea Cetaceans > The air Bats > Highest mountains Pika & Marmots > Hottest deserts Swift fox > Coldest regions Polar bears & Seals
